The ER-Holder Simple Spindle

log

This is a simple spindle for simple milling machines, that we can make with a 3D Printer and some off-the-shelf parts.

It uses a 'collet holder' (which can be found on ebay) with two simple roller bearings on either end to form the main mechanism. See! Simple. Drive that with a BLDC motor, and you're milling.

Notes

The belleville washers (disk springs) included in the BOM should be mounted between the collet-holder collet-holding end and the inner race of the bottom bearing. The 40T pulley w/ respective set-screws holds the collet holder into the bearing / body assembly - as you tighten those screws, try to compress those belleville washers. This way the bearings are a little bit preloaded, which helps them run smooth / for a long time / quitely. S/O to Ilan Moyer for this tip.

Runout

I measured a runout at the collet holder of ~ 1 thousandths, and at the tip of a 1/8" tool around ~ 3 thousandths. That's OK for $150 in parts, and a plastic housing.

spindle test

BOM

This is a short list of parts for the latest design as of 2020 07 10 as implemented on clank.